Fuel-fired burners or combustors can be used to regenerate particulate filters in soot abatement assemblies. The fuel fired combustor includes a combustion chamber that receives at least a portion of exhaust gas flow from a vehicle engine, a fuel inlet, an air inlet, and an igniter. During vehicle operation, soot accumulates on the particulate filter. As soot accumulation increases, the operating efficiency of the vehicle engine can be adversely affected. Once the amount of soot in the particulate filter reaches a certain level, the igniter is used to ignite a fuel/air/exhaust gas mixture forming a flame that increases the temperature to a set-point such that the soot can be burned off resulting in regeneration of the filter.
Once the flame is detected in a fuel-fired combustor, it is important to ensure that the flame is maintained during the entire fueling cycle. If the flame is extinguished unexpectedly, there could be significant gaseous emissions emitted by the combustor.
Further, if an inlet pipe into the fuel-fired combustor breaks or detaches from the combustor, an uncontrolled flame could be exposed to the ambient environment. If the fuel-fired combustor fails such that the flame from combustion is exposed, damage to the surrounding components could occur.
Once the ignition phase of the fuel-fired combustor is complete and the flame is present, it is important for a control system to begin the next stage of fueling by ramping the temperature up to the set-point. If the fuel rate is too low, the flame may be extinguished, and if the rate is too high, there may be increased levels of emissions and downstream components may overheat.
The temperature of the fuel supplied to the combustor is directly related to a size of the fuel droplets when the fuel is atomized. The colder the fuel is, the bigger the droplets are. Bigger droplets are more difficult to ignite than smaller droplets. Further, the colder the exhaust gas is flowing into the combustor, the more fuel it takes to achieve the same set-point temperature.